Method for aligning thin film head pole tips

ABSTRACT

A thin film magnetic read/write head is manufactured using Al 2  O 3  dams. The Al 2  O 3  dams are formed using a sacrificial layer which is deposited upon a bottom pole layer. An Al 2  O 3  layer is deposited over the sacrificial layer. When the sacrificial layer is removed, the Al 2  O 3  layer forms dams between which a top pole piece is deposited. The sacrificial layer is removed using lapping and a selected chemical etch; partial lapping or chemical etch followed by chemical etch of the sacrificial layer which lifts-off overlying Al 2  O 3  ; depositing photoresist dams and chemically etching the encapsulation layer and the sacrificial layer; or removal through physical or thermal shock of the Al 2  O 3  layer sputtered at zero bias followed by a selective chemical etch of the sacrificial layer.

BACKGROUND OF THE INVENTION

The present invention relates to production of thin film magnetic heads.In particular, the invention relates to aligning the upper and lowerpole tips in a thin film magnetic head using a sacrificial layer.

Thin film magnetic read/write heads are used for magnetically readingand writing information upon a magnetic storage medium such as amagnetic disc or a magnetic tape. It is highly desirable to provide ahigh density of information storage on the magnetic storage medium.

Increased storage density in a recording system may be achieved byproviding an areal density as high as possible for a given recordingsurface. In the case of rotating disc drives (both floppy and harddisc), the areal density is found by multiplying the number of bits perunit length along the track (linear density in units of bits per inch)by the number of tracks available per unit length in the radialdirection (track density in units of tracks per inch).

The demand for increased storage density in magnetic storage media hasled to reduced magnetic head dimensions. Magnetic heads are nowfabricated in a manner similar to that used for semiconductor integratedcircuits in the electronic industry.

During fabrication, many thin film magnetic heads are deposited acrossthe surface of a wafer (or substrate). After the layers are deposited,the wafer is "diced" or sliced into many individual thin film heads,each carried by a portion of the wafer so that an upper pole tip, alower pole tip, and a gap are exposed. The pole tips and the gap (andthe portion of the substrate which underlies them) are then lapped in adirection generally inward, toward the center of thin film head, toachieve the desired dimensions. This lapping process is a grindingprocess in which the exposed portion of the top and bottom pole tips andthe gap are applied to an abrasive, such as a diamond slurry. Electricalcontacts are connected to conductive coils. The completed head isattached to a carrying fixture for use in reading and writing data on amagnetic storage medium such as a computer disc.

In operation, the exposed upper and lower pole tips are positioned neara moving magnetic storage medium. During the read operation, thechanging magnetic flux of the moving storage medium impresses a changingmagnetic flux upon upper and lower pole tips. The magnetic flux iscarried through the pole tips and yoke core around the conductor coil.The changing magnetic flux induces an electrical voltage across theconductor coil which may be detected with electrical detectioncircuitry. The electrical voltage is representative of the changingmagnetic flux produced by the moving magnetic storage medium.

During a write operation, an electrical current is caused to flow in theconductor coil. This electric current induces a magnetic field in topand bottom magnetic poles and causes a magnetic field across the gapbetween the upper and lower pole tips. A fringe field extends in thevicinity beyond the boundary of the pole tips and into the nearbymagnetic storage medium. This fringe field may be used to impressmagnetic fields upon the storage medium and magnetically writeinformation.

The highest track density achievable is strongly influenced by theaccuracy and precision of alignment of upper and lower pole tips andtheir width. Magnetic pole tips typically have a pole thickness in therange of about one micrometer to about five micrometers depending upondesign criteria, i.e. a thicker pole for better overwriting efficiencyand a thinner pole for increased resolution capability during thereadback operation.

As track density increases, currently approaching and exceeding 2400tracks per inch, the alignment between the upper and lower pole tips inthin film magnetic read/write heads has become critical. At such a highstorage density, design criteria require magnetic transducers in whichthe bottom pole tip width is very nearly the same as the top pole tipwidth. Top and bottom pole tips should also be in close alignment. Atthese small dimensions, alignment between the pole tips of a headbecomes critical, particularly as dimensions of the pole tips approachthe tolerance and definition limits of the deposition techniques. Atechnique which provides better pole alignment begins with a top pole,bottom pole and a gap area separating the top and bottom poles, allfabricated substantially wider than desired. A narrower mask layer isthen deposited upon the upper pole. The structure is then aligned usinga material removal process ("milling") such as ion milling or reactiveion milling in which high energy ions bombard the pole tip region toremove the excess material (top pole, bottom pole and gap material) thatextends beyond the edges of the mask layer. The mask layer protects onlya portion of the top pole, bottom pole and gap so that the width of thecompleted pole tips is approximately the same as the width of the masklayer.

The noted alignment technique suffers from a number of drawbacks. Themask layer is difficult to remove from the pole tip structure after themilling process. To ensure adequate protection of the pole tips duringmilling, the mask must be very thick to withstand the milling process. Athick mask, however, decreases the ability to control the shape of thepole tips. Furthermore, if the remaining mask material is stripped awayfollowing milling, the delicate structure of the thin film head may bedamaged. If, on the other hand, the mask layer is made thinner toimprove process control and facilitate removal of the mask following ionmilling, the risk of damaging the pole tip structure during milling isincreased.

An accurate and precise method of aligning pole tips would be animportant contribution to the art.

SUMMARY OF THE INVENTION

The present invention provides closely aligned pole tips in a thin filmmagnetic transducer. This may be used to yield increased data storagedensities. In the present invention, the top pole is aligned with thebottom pole using dams made with the aide of a sacrificial layer. Thedams are formed by depositing an encapsulation layer over a sacrificiallayer. The sacrificial layer is deposited in substantially selfalignment with the bottom pole. When the sacrificial layer is removed,the encapsulation layer which overlies the sacrificial layer "lifts off"from the surface. Following the removal of the sacrificial layer, theresultant empty cavity in the encapsulation layer forms edges of thedams. The sacrificial layer is removed through any suitable alternative.These alternatives include lapping, selective chemical etching,lift-off, and removing through thermal or physical shock. The cavity isfilled with magnetic material to form the top pole. A magnetic gap isformed between the top pole and the bottom pole.

In the present invention, photoresist dams are deposited upon asubstrate which carries the thin film magnetic head. A bottom pole isdeposited between the photoresist dams. A sacrificial layer is depositedbetween the photoresist dams upon the bottom pole. Typically, thesacrificial layer is a layer of copper. Next, the photoresist dams areremoved and the pole tip region is coated with an encapsulation layer,typically of Al₂ O₃. In accordance with the present invention, theencapsulation layer which covers the sacrificial layer is removed alongwith the sacrificial layer. Following this removal, the encapsulationlayer forms dams on either side of the bottom pole. The dams extendabove the sides of the bottom pole. Next, a gap layer is deposited overthe bottom pole layer. Typically the gap layer comprises Al₂ O₃.Additional photoresist dams are deposited upon the gap Al₂ O₃ layer andare generally in alignment with the bottom pole. A top pole layer isdeposited upon the gap Al₂ O₃ layer. The top pole is aligned with thebottom pole by the dams formed by the encapsulation layer.

In accordance with the present invention, the encapsulation layer whichoverlies the bottom pole and covers the sacrificial layer may be removedusing a number of techniques. The encapsulation layer can be removedusing a lapping process. In the lapping process, the pole tip region islapped so that the encapsulation layer is removed and the sacrificiallayer is exposed. The sacrificial layer is selectively etched whichleaves dams extended above either side of the bottom pole.

The overlying encapsulation layer can also be removed using a lift-offprocess. The encapsulation layer is deposited by a sputtering techniquein which a sufficiently negative electrical bias potential andsufficiently high gas pressure are used to reduce deposition of theencapsulation layer at the corners of sacrificial layer. Followingdeposition of the encapsulation layer, a small amount of ion milling orchemical etching will expose the edges of sacrificial layer under theencapsulation layer. The overlying encapsulation layer is removedthrough lift-off using a selective chemical etch for the sacrificiallayer. Again, dams are formed from the encapsulation layer which arealigned with the lower pole. The top pole may be deposited as describedabove.

The encapsulation layer can be removed by depositing photoresist dams onthe encapsulation layer which leave a portion of the encapsulation layerexposed. A selective chemical etch is applied which etches the exposedportion of the encapsulation layer. The sacrificial layer and thephotoresist dams are removed. Again, dams are formed from theencapsulation layer which are aligned with the lower pole. The top polemay be deposited as described above.

The encapsulation layer can also be removed by physical or thermalshock. If the encapsulation layer is sputtered upon the surface with azero electrical bias potential, it will adhere poorly to the sacrificiallayer. The structure can then be subjected to physical or thermal shockswhich cause the overlying encapsulation layer to break free of thesacrificial layer. The sacrificial layer is selectively chemicallyetched and the top pole is deposited between the dams formed by theencapsulation layer and in alignment with the lower pole.

The present invention provides dams which are aligned with the bottompole which can be used to deposit the top pole. The dams are formed inan encapsulation layer with a sacrificial layer. The encapsulation layerwhich overlies the sacrificial layer is removed using three alternativeprocesses. Al₂ O₃ provides an excellent encapsulation layer materialbecause Al₂ O₃ is nonmagnetic and residual Al₂ O₃ will not degrade thinfilm head operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of a thin film magnetic read/write head.

FIG. 2 is a side cross sectional view of the thin film magnetic head ofFIG. 1 taken along line 2--2.

FIG. 3A is a cross-sectional view of a substrate.

FIG. 3B is a cross-sectional view of the substrate of FIG. 3A includingphotoresist dams.

FIG. 3C is a cross-sectional view of a substrate including a lower polepiece.

FIG. 3D is a cross-sectional view of a substrate which includes asacrificial layer.

FIG. 3E is a cross-sectional view of a substrate following removal ofphotoresist dams.

FIG. 3F is a cross-sectional view of a substrate following deposition ofan Al₂ O₃ layer.

FIG. 4A is a cross-sectional view of a substrate following a lappingprocess.

FIG. 4B is cross-sectional view of a substrate following removal of asacrificial layer.

FIG. 4C is cross-sectional view of a substrate following deposition ofan Al₂ O₃ gap layer.

FIG. 4D is cross-sectional view following deposition of photoresistdams.

FIG. 4E is a cross-sectional view of a substrate following deposition ofa top pole piece.

FIG. 4F is a cross-sectional view of FIG. 1 taken along line 4F--4F.

FIG. 5A is a cross-sectional view of a substrate which shows anencapsulation layer.

FIG. 5B is a cross-sectional view of a substrate including anencapsulation layer and a partially exposed sacrificial layer.

FIG. 6A is a cross-sectional view of a substrate which shows anencapsulation layer and photoresist dams.

FIG. 6B is a cross-sectional view of a substrate including photoresistdams and a partially exposed sacrificial layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A multi-turn inductive thin film magnetic head 10 is shown schematicallyin FIGS. I and 2. FIG. 1 is a top view of thin film head 10 and FIG. 2is a side cross sectional view. Thin film head 10 includes top pole 12and bottom pole 14 magnetic thin film core which comprise a nickel-iron(NiFe) alloy. Photolithography is used to define the geometry of bothtop pole 12 and bottom pole 14 of the magnetic core. Conductive coils 16and 18 extend between top and bottom magnetic thin film poles 12 and 14and are electrically insulated from magnetic core poles 12 and 14 by aninsulating layer 20. Thin film head 10 is deposited upon a nonmagneticsubstrate 22 which comprises a ceramic composite compound, such as Al₂O₃ -TiC.

In fabricating thin film head 10, several separate pattern transferprocesses are used to deposit head 10 upon substrate 22. These transferprocesses include chemical etching, plating and sputtering. A typicalhead fabrication process may account for more than a dozen maskinglevels and more than thirty processing steps.

FIGS. 3A-3F show the initial steps of pole tip alignment used in thepresent invention. FIG. 3A is a cross-sectional view of ceramicsubstrate 22. Ceramic substrate 22 forms the base upon which thin filmhead 10 (shown in FIG. 2) is fabricated.

FIG. 3B is a cross-sectional view of substrate 22 including photoresistdams 30A and 30B. Photoresist dams 30A and 30B are formed by depositinga layer of photoresist across the surface of substrate 22. A portion ofthe photoresist layer is exposed to ultraviolet radiation. A specialchemical etch is applied which removes the portion of the photoresistwhich was exposed to the radiation.

FIG. 3C is a cross-sectional view of substrate 22 with photoresist dams30A and 30B and a bottom pole 32. Bottom pole 32 comprises NiFe.Photoresist dams 30A and 30B define the edges of bottom pole 32.

FIG. 3D is a cross-sectional view of substrate 22 which shows asacrificial layer 34. Sacrificial layer 34 is deposited upon bottom pole32 between photoresist dams 30A and 30B. Photoresist dams 30A and 30Bdefine the edges of sacrificial layer 34. In a preferred embodiment,sacrificial layer 34 comprises copper. As shown in FIG. 3D, becausesacrificial layer 34 is deposited using photoresist dams 30A and 30Bused to deposit bottom pole 32, sacrificial layer 34 is in substantialalignment with bottom pole 32.

FIG. 3E shows another step in the process of the present invention. InFIG. 3E, photoresist dams 30A and 30B have been stripped away.Photoresist dams 30A and 30B are stripped using a selective chemicaletch which attacks only the photoresist dams 30A and 30B. The chemicaletch leaves bottom pole 32 and sacrificial layer 34 substantially intactas shown in FIG. 3E.

FIG. 3F is a cross-sectional view of substrate 22 following depositionof an encapsulation layer 36. Encapsulation layer 36 preferablycomprises Al₂ O₃. Encapsulation layer 36 is deposited across the surfaceof substrate 22 and substantially encapsulates bottom pole 32 andsacrificial layer 34 as depicted in FIG. 3F. Encapsulation layer 36 maybe deposited using a sputtering technique. The electrical bias and gaspressure applied during the sputtering process changes characteristicsof the encapsulation layer 36.

In accordance with the present invention, after the steps shown in FIGS.3A through 3F, sacrificial layer 34 may be removed using a suitableprocedure to leave the edges of encapsulation layer 36 substantiallyintact. Encapsulation layer 36 forms two dams used in a subsequentdeposition process. Between the two dams an upper pole is depositedwhich is in substantial alignment with the bottom pole.

FIGS. 4A through 4F show the steps of one alternative process forremoving the sacrificial layer through lapping and selective chemicaletching. In FIG. 4A, a cross-sectional view of substrate 22,encapsulation layer 36 has been lapped to expose a surface ofsacrificial layer 34. The lapping process is a process in which asurface is applied to an abrasive which wears the surface down. In FIG.4A, encapsulation layer 36 has been lapped to expose sacrificial layer34 without substantially removing sacrificial layer 34. Following thelapping process, encapsulation layer 36 forms two separate pieces, dam36A and dam 36B.

FIG. 4B shows a cross-sectional view of substrate 22 following aselective chemical etch of sacrificial layer 34. For example, ifsacrificial layer 34 comprises copper, a selective chemical etch wouldbe applied which attacks only copper and does not significantly alterlower pole 32 and dams 36A and 36B.

FIG. 4C is a cross-sectional view of substrate 22 including a gap layer38. Typically, gap layer 38 comprises Al₂ O₃. In a preferred embodiment,this gap layer 38 comprises the same material as dams 36A and 36B. Gaplayer 38 is a non-magnetic material which forms a magnetic gap used inthe thin film head.

FIG. 4D is a cross-sectional view of substrate 22 including photoresistdams 40A and 40B. Photoresist dams 40A and 40B are used in forming a toppole 42 (shown in FIG. 4E). The alignment of photoresist dams 40A and40B with lower pole 32 is not as critical as the alignment of dams 36Aand 36B with lower pole 32. Photoresist dams 40A and 40B are depositedusing a layer of photoresist which is selectively exposed to activatingradiation and then chemically etched.

FIG. 4E shows a cross-sectional view of substrate 22 including upperpole 42. Upper pole 42 is deposited upon gap layer 38 and in substantialalignment with bottom pole 32. Dams 36A and 36B provide a closealignment between upper pole 42 and lower pole 32. The photoresist dams40A and 40B also contain the outer edges of upper pole 42. Typically,upper pole 42 comprises NiFe. Upper pole 42 is used to complete amagnetic flux circuit between upper pole 42 and lower pole 32 across gaplayer 38.

FIG. 4F is a cross-sectional view of substrate 22 following removal ofphotoresist dams 40A and 40B. FIG. 4F shows a substantially completecross-sectional view of thin film head 10 shown in FIG. 1 taken alongline 4F--4F. Typically, the structure of FIG. 4F is encapsulated in anon-magnetic material such as Al₂ O₃. Dams 36A and 36B remain depositedupon substrate 22 after completion of the fabrication process.

FIG. 5A shows another alternative embodiment of forming dams with asacrificial layer in accordance with the present invention. FIG. 5A is across-sectional view of substrate 22. In FIG. 5A an encapsulation layer44 is deposited upon lower pole 32 and sacrificial layer 34. Typically,encapsulation layer 44 comprises Al₂ O₃, a non-magnetic material.Encapsulation layer 44 is sputtered upon substrate 22 and sacrificiallayer 34. During the sputtering process, an electrical bias potential isapplied which is sufficiently negative to form a incline inencapsulation layer 44 at corners 46A and 46B of sacrificial layer 34.For example, electrical bias between the substrate and the source shouldbe between about -100 volts and about -160 volts, which is about 10% to16% of the target voltage. Gas pressure should be about 10 milliTorr to20 milliTorr. These parameters depend upon characteristics of thedeposition process. In FIG. 5A, encapsulation layer 44 is relativelythin near corners 46A and 46B of sacrificial layer 34.

FIG. 5B shows a cross-sectional view of substrate 22 in which corners46A and 46B of sacrificial layer 34 are exposed through encapsulationlayer 44. Corners 46A and 46B of encapsulation layer 44 are exposed byslightly ion milling encapsulation layer 44 shown in FIG. 5A or byapplying a mild chemical etch to encapsulation layer 44. Alternatively,the electrical bias applied during sputtering and the amount of materialsputtered down may be adjusted so that corners 46A and 46B are notcompletely covered by encapsulation layer 44. In either case, oncecorners 46A and 46B of encapsulation 44 are exposed, a selectivechemical etch can be applied to sacrificial layer 34. For example, ifsacrificial layer 34 comprises copper, a copper chemical etch can beapplied. This lifts off the portion 44C of encapsulation layer 44 whichoverlies sacrificial layer 34. The result and cross-sectional view issimilar to the cross-sectional view shown in FIG. 4B. Subsequent stepscan be followed to fabricate an upper pole 42 as shown FIGS. 4C through4F.

FIGS. 6A and 6B show another alternative embodiment of forming dams witha sacrificial layer in accordance with the present invention. FIG. 6Ashows a cross-sectional view of a substrate 22 in which lower pole 32and sacrificial layer 34 is covered by an encapsulation layer 48. InFIG. 6A, photoresist dams 50A and 50B partially cover encapsulationlayer 48 and leave a portion of encapsulation layer 48 exposed. Aselective chemical etch is applied to encapsulation layer 48 whichselectively etches only the material of encapsulation layer 48. Thisforms encapsulation layer dams 48A and 48B shown in FIG. 6. Photoresistdams 50A and 50B are chemically stripped. Sacrificial layer 34 isselectively etched. This leaves an encapsulation layer dam structuresimilar to that shown in FIG. 4B. The cavity formed betweenencapsulation layer dams 48A and 48B may be filled with a top pole pieceas described above.

In another alternative process for removing the portion of theencapsulation layer which overlies the sacrificial layer, theencapsulation layer is sputtered using an electrical bias of zero volts.Gas pressure should be about 20 to about 30 milliTorr. These parametersdepend upon the sputtering mechanism. This causes the encapsulationlayer to weakly adhere to the sacrificial layer. The portion of theencapsulation layer which overlies the sacrificial layer may be removedby subjecting the structure to physical or thermal shocks. The physicalor thermal shocks cause the encapsulation layer to break free from thesacrificial layer and leave behind dams on either side of the lowerpole. The sacrificial layer can be removed using a selective chemicaletch as described above.

The present invention provides a method of fabricating closely alignedpole tips in a thin film magnetic head. In the present invention, a toppole is aligned with a bottom pole using dams made with a sacrificiallayer. The dams are formed by depositing an encapsulation layer over thesacrificial layer. When the sacrificial layer is removed, theencapsulation layer which overlies the sacrificial layer is removed.This provides two dams formed from the encapsulation layer on eitherside of the bottom pole. These dams are used to form the top pole insubstantial alignment with the bottom pole.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, the encapsulation layer andsacrificial layer may be formed using any suitable material such as aceramic, a glass or Si, and the steps of forming dams with theencapsulation by removing the sacrificial layer may be through anysuitable means. Furthermore, the sacrificial layer may comprise anysuitable selectively etchible layer and the magnetic layers may comprisemagnetic material other than NiFe.

What is claimed is:
 1. A method of manufacturing a thin film magnetichead comprising:depositing an elongated bottom pole layer having a gapface and side edges over a substrate, the gap face for magneticallycoupling with a magnetic storage medium; depositing a sacrificial layerhaving side edges over the bottom pole layer, wherein the side edges arein substantial alignment with the side edges of the bottom pole layer;depositing an encapsulation layer over the sacrificial layer and thesubstrate; removing the sacrificial layer and a portion of theencapsulation layer to form first and second dams from the encapsulationlayer having edges, wherein the edges of the first and second dams arein substantial alignment with the side edges of the bottom pole layer;and depositing an elongated upper pole layer having a gap face and sideedges between the edges of the first and second dams and over the bottompole layer, the gap face for magnetically coupling with a magneticstorage medium, wherein the side edges of the upper pole layer are insubstantial alignment with the side edges of the bottom pole layer andare defined by the edges of the first and second dams.
 2. The method ofclaim 1 wherein depositing an encapsulation layer comprises depositing alayer of Al₂ O₃.
 3. The method of claim 1 wherein depositing asacrificial layer comprises depositing a copper layer.
 4. The method ofclaim 1 wherein removing the sacrificial layer comprises lapping aportion of the encapsulation layer in a direction normal to thesubstrate followed by chemically etching the sacrificial layer.
 5. Themethod of claim 1 wherein removing the sacrificial layer comprisesapplying a chemical etch to the sacrificial layer wherein thesacrificial layer is removed and a portion of the encapsulation layerwhich overlies the sacrificial layer is lifted off.
 6. The method ofclaim 1 wherein removing a portion of the encapsulation layercomprises:depositing a first photoresist dam having an edge and a secondphotoresist dam having an edge upon the encapsulation layer, wherein theedges of the first and second photoresist dams are in substantialalignment with the side edges of the bottom pole layer; applying aselective chemical etch to the encapsulation layer between the edges ofthe first and second photoresist dams wherein a portion of theencapsulation layer is removed to form the first and second dams; andremoving the first photoresist dam and the second photoresist dam. 7.The method of claim 1 wherein removing the sacrificial layer comprisessubjecting the encapsulation layer to a shock whereby a portion of theencapsulation layer which overlies the sacrificial layer is removed,followed by applying a selective chemical etch to the sacrificial layer.8. The method of claim 1 including depositing a gap layer over thebottom pole layer following removing the sacrificial layer.
 9. Themethod of claim 1 including encapsulating the lower pole layer and theupper pole layer with a non-magnetic material following the step ofdepositing an upper pole layer.
 10. The method of claim 1 whereindepositing an encapsulation layer comprises sputtering the encapsulationlayer.
 11. A method of manufacturing a thin film magnetic headcomprising:depositing a first photoresist dam having an edge and asecond photoresist dam having an edge upon a substrate; depositing anelongated bottom pole layer having a gap face and side edges over thesubstrate and between the edges of the first and second photoresistdams, the gap face of the bottom pole layer for magnetically couplingwith a magnetic storage medium, wherein the side edges are defined bythe edges of the first and second photoresist dams; depositing asacrificial layer having side edges over the bottom pole and between theedges of the first and second photoresist dams, wherein the side edgesof the sacrificial layer are defined by the edges of the first andsecond photoresist dams and are in substantial alignment with the sideedges of the bottom pole layer; removing the first and secondphotoresist dams; depositing an encapsulation layer over the sacrificiallayer and the substrate; removing the sacrificial layer and a portion ofthe encapsulation layer to form a first encapsulation layer dam and asecond encapsulation layer dam from the encapsulation layer wherein thefirst and second encapsulation layer dams have edges which are insubstantial alignment with the side edges of the bottom pole layer;depositing a third photoresist dam having an edge over the firstencapsulation layer dam; depositing a fourth photoresist dam having anedge over the second encapsulation layer dam; depositing an elongatedupper pole layer having a gap face and side edges between the edges ofthe first and second encapsulation layer dams and between the edge ofthe third and fourth photoresist dams and over the bottom pole layer,the gap face of the upper pole layer for magnetically coupling with amagnetic storage medium, wherein the side edges of upper pole layer aredefined by the edges of the first and second encapsulation layer damsand are in substantial alignment with the side edges of the bottom polelayer; and removing the third and fourth photoresist dams.
 12. Themethod of claim 11 wherein depositing an encapsulation layer comprisesdepositing a layer of Al₂ O₃.
 13. The method of claim 11 whereindepositing a sacrificial layer comprises depositing a copper layer. 14.The method of claim 11 wherein removing the sacrificial layer compriseslapping a portion of the encapsulation layer in a direction normal tothe substrate followed by chemically etching the sacrificial layer. 15.The method of claim 12 wherein removing a portion of the encapsulationlayer comprises:depositing a first photoresist dam having an edge and asecond photoresist dam having an edge upon the encapsulation layer,wherein the edges of the first and second photoresist dams are insubstantial alignment with the side edges of the bottom pole layer;applying a selective chemical etch to the encapsulation layer betweenthe edges of the first and second photoresist dams wherein a portion ofthe encapsulation layer is removed to form the first and second dams;and removing the first photoresist dam and the second photoresist dam.16. The method of claim 11 wherein removing the sacrificial layercomprises applying a chemical etch to the sacrificial layer wherein thesacrificial layer is removed and a portion of the encapsulation layerwhich overlies the sacrificial layer is lifted off.
 17. The method ofclaim 11 wherein removing the sacrificial layer comprises subjecting theencapsulation layer to a shock whereby a portion of the encapsulationlayer which overlies the sacrificial layer is removed, followed byapplying a selective chemical etch to the sacrificial layer.
 18. Themethod of claim 11 including depositing a gap layer over the bottom polelayer following removing the sacrificial layer.
 19. The method of claim11 including encapsulating the lower pole layer and the upper pole layerwith a non-magnetic material following the step of depositing an upperpole layer.
 20. The method of claim 11 wherein depositing anencapsulation layer comprises sputtering the encapsulation layer.